499 research outputs found
Nanodiamonds for Field Emission: State of the Art
The aim of this review is to highlight the recent advances and the main remaining challenges related to
the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic
devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties
of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies
and further benefits can be obtained by tailored improvements of processing methodologies. The
current strategies used to modulate the morphological and structural features of diamond to produce
highly performing emitting systems are reported and discussed. The focus is on the current understanding
of the FE process from nanodiamond-based materials and on the major concepts used to improve their
performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is
also reported
Si/C hybrid nanostructures for Li-ion anodes : am overview
This review article summarizes recent and increasing efforts in the development of novel Li ion cell
anode nanomaterials based on the coupling of C with Si. The rationale behind such efforts is based on the
fact that the SieC coupling realizes a favourable combination of the two materials properties, such as the
high lithiation capacity of Si and the mechanical and conductive properties of C, making Si/C hybrid
nanomaterials the ideal candidates for innovative and improved Li-ion anodes. Together with an overview
of the methodologies proposed in the last decade for material preparation, a discussion on relationship
between organization at the nanoscale of the hybrid Si/C systems and battery performances is
given. An emerging indication is that the enhancement of the batteries efficiency in terms of mass capacity,
energy density and cycling stability, resides in the ability to arrange Si/C bi-component nanostructures
in pre-defined architectures. Starting from the results obtained so far, this paper aims to
indicate some emerging directions and to inspire promising routes to optimize fabrication of Si/C
nanomaterials and engineering of Li-ion anodes structures. The use of Si/C hybrid nanostructures could
represents a viable and effective solution to the foreseen limits of present lithium ion technology.
2013 Published by Elsevier
Characterization of polyaniline-detonation nanodiamond nanocomposite fibers by atomic force microscopy based technique
Polyaniline (PANI) fibers were synthesized in presence of detonantion nanodiamond (DND) particles by precipitation polymerization technique. Morphological, electrical and mechanical characterizations of the obtained PANI/DND nanocomposited have been performed by different either standard or advanced atomic force microscopy (AFM) based techniques. Morphological characterization by tapping mode AFM supplied information about the structure of fibers and ribbons forming the PANI/DND network. An AFM based technique that takes advantage of an experimental configuration specifically devised for the purpose was used to assess the electrical properties of the fibers, in particular to verify their conductivity. Finally, mechanical characterization was carried out synergically using two different and recently proposed AFM based techniques, one based on AFM tapping mode and the other requiring AFM contact mode, which probed the nanocomposited nature of PANI/DND fiber sample down to different depths. © 2013 Elsevier Ltd. All rights reserved
Atomic force microscopy techniques for nanomechanical characterization : a polymer case study
Atomic force microscopy (AFM) is a versatile tool to perform mechanical
characterization of surface samples at the nanoscale. In this work, we review
two of such methods, namely contact resonance AFM (CR-AFM) and torsional
harmonics AFM (TH-AFM). First, such techniques are illustrated and their
applicability on materials with elastic moduli in different ranges are discussed,
together with their main advantages and limitations. Then, a case
study is presented in which we report the mechanical characterization using
both CR-AFM and TH-AFM of polyaniline and polyaniniline doped with
nanodiamond particles tablets prepared by a pressing process. We determined
the indentation modulus values of their surfaces, which were found in fairly
good agreement, thus demonstrating the accuracy of the techniques. Finally,
the determined surface elastic moduli have been compared with the bulk ones
measured through standard indentation testing.
INTRODUCTION
In the field of nanotechnology, the development of
innovative and nondestructive characterization
techniques plays a crucial role. Indeed, the characterization
of nanostructured hybrid materials (e.g.,
thin films and nanocomposites) and devices requires
the capability of acquiring maps of the local mechanical
properties at the nanoscale. Nanoindentation
is the most common method for determining the
mechanical properties of thin films. However, its
applicability is strictly limited by the thickness of
the sample. Furthermore, its poor spatial resolution
does not allow the reconstruction of an accurate
distribution of the sample surface mechanical
properties. For this reason, alternative methods,
based on atomic force microscopy (AFM), have been
developed. By exploiting the high resolution of the
AFM, maps of the surface mechanical properties
(i.e., indentation modulus) can be achieved. Among
these techniques, AFM nanoindentation1 is the
simplest method used to evaluate the local mechanical
properties o
Nanocarbon surfaces for biomedicine
The distinctive physicochemical, mechanical and electrical
properties of carbon nanostructures are currently gaining
the interest of researchers working in bioengineering and
biomedical fields. Carbon nanotubes, carbon dendrimers, graphenic
platelets and nanodiamonds are deeply studied aiming
at their application in several areas of biology and medicine.
Here we provide a summary of the carbon nanomaterials
prepared in our labs and of the fabrication techniques used to
produce several biomedical utilities, from scaffolds for tissue
growth to cargos for drug delivery and to biosensors
Detonation nanodiamonds tailor the structural oeder of PEDOT chains in conductive coating layers of hybrid nanoparticles
Solid layers of PEDOT–detonation nanodiamond based nanoparticles with an exceptional structural order
were produced by means of a template-free polymerization technique. As an efficient multifunctional filler,
the nanocrystalline diamond has been shown to possess a high catalytic activity on the monomer
polymerization rate as well as to play a fundamental role as a 3D arrangement-directing agent of the
PEDOT chains at the micro- and nano-scale. SEM, TEM and TED analyses highlighted the mutual
organization between PEDOT oligomers and nanodiamond grains, and the produced hierarchical effects
on the arrangement of the backbones of the final polymer. Optical and Raman spectroscopy, used
together with XRD diffraction to study the molecular structure and crystallographic features of the hybrid
materials, pointed out that the adopted synthetic strategy enables highly conjugated and doped hybrid
systems to be generated. The spatial distribution of the filler inside the polymeric matrix and the mutual
connectivity of nanodiamond crystals and PEDOT segments are found to strongly improve the functional
properties of the host polymer. Mechanical characterizations by advanced AFM-based techniques
revealed that both indentation modulus and hardness of PEDOT/nanodiamond materials are 3 times
higher than the pure PEDOT polymer, while electrical characterizations by a 4-probe method gave sheet
resistance values of 1 106 U sq 1 for the nanocomposite particle
Laminin γ1 chain peptide, C-16 (KAFDITYVRLKF), promotes migration, MMP-9 secretion, and pulmonary metastasis of B16–F10 mouse melanoma cells
Laminin-1, a heterotrimer of α1, β1, and γ1 chains specific to basement membrane, promotes cell adhesion and migration, proteinase secretion and metastases of tumour cells. Several active sites on the α1 chain have been found to promote B16–F10 melanoma lung colonisation and here we have determined whether additional tumour promoting sites exist on the β1 and γ1 chains. Recently, we have identified novel cell adhesive peptides derived from laminin β1 and γ1 chains by systematic screening of synthetic peptides. Nine β1 peptides and seven γ1 peptides active for cell adhesion were tested for their effects on experimental pulmonary metastases of B16–F10 mouse melanoma cells in vivo. The most active adhesive peptide derived from the γ1 chain globular domain, C-16 (KAFDITYVRLKF), significantly enhanced pulmonary metastases of B16–F10 cells, whereas no other peptides showed enhancement. C-16 also stimulated migration of B16–F10 cells in the Boyden chamber assay in vitro. Furthermore, C-16 significantly induced the production of MMP-9 from B16–F10 cells. These results suggest that this specific laminin γ1 chain peptide has a metastasis-promoting activity and might be a new molecular target of anti-cancer treatment
A Trouble Shared Is a Trouble Halved: Social Context and Status Affect Pain in Mouse Dyads
In mice behavioral response to pain is modulated by social status. Recently, social context also has been shown to affect pain sensitivity. In our study, we aimed to investigate the effects of interaction between status and social context in dyads of outbred CD-1 male mice in which the dominance/submission relationship was stable. Mice were assessed for pain response in a formalin (1% concentration) test either alone (individually tested-IT), or in pairs of dominant and subordinate mice. In the latter condition, they could be either both injected (BI) or only one injected (OI) with formalin. We observed a remarkable influence of social context on behavioral response to painful stimuli regardless of the social status of the mice. In the absence of differences between OI and IT conditions, BI mice exhibited half as much Paw-licking behavior than OI group. As expected, subordinates were hypoalgesic in response to the early phase of the formalin effects compared to dominants. Clear cut-differences in coping strategies of dominants and subordinates appeared. The former were more active, whereas the latter were more passive. Finally, analysis of behavior of the non-injected subjects (the observers) in the OI dyads revealed that dominant observers were more often involved in Self-grooming behavior upon observation of their subordinate partner in pain. This was not the case for subordinate mice observing the pain response of their dominant partner. In contrast, subordinate observers Stared at the dominant significantly more frequently compared to observer dominants in other dyads. The observation of a cagemate in pain significantly affected the observer's behavior. Additionally, the quality of observer's response was also modulated by the dominance/submission relationship
Maximizing the general success of cecal intubation during propofol sedation in a multi-endoscopist academic centre
<p>Abstract</p> <p>Background</p> <p>Achieving the target of 95% colonoscopy completion rate at centres conducting colorectal screening programs is an important issue. Large centres and teaching hospitals employing endoscopists with different levels of training and expertise risk achieving worse results. Deep sedation with propofol in routine colonoscopy could maximize the results of cecal intubation.</p> <p>Methods</p> <p>The present study on the experience of a single centre focused on estimating the overall completion rate of colonoscopies performed under routine propofol sedation at a large teaching hospital with many operators involved, and on assessing the factors that influence the success rate of the procedure and how to improve this performance, analyzing the aspects relating to using of deep sedation. Twenty-one endoscopists, classified by their level of specialization in colonoscopic practice, performed 1381 colonoscopies under deep sedation. All actions needed for the anaesthesiologist to restore adequate oxygenation or hemodynamics, even for transient changes, were recorded.</p> <p>Results</p> <p>The "crude" overall completion rate was 93.3%. This finding shows that with routine deep sedation, the colonoscopy completion rate nears, but still does not reach, the target performance for colonoscopic screening programs, at centers where colonoscopists of difference experience are employed in such programs.</p> <p>Factors interfering with cecal intubation were: inadequate colon cleansing, endoscopists' expertise in colonoscopic practice, patients' body weight under 60 kg or age over 71 years, and the need for active intervention by the anaesthesiologist. The most favourable situation - a patient less than 71 years old with a body weight over 60 kg, an adequate bowel preparation, a "highly experienced specialist" performing the test, and no need for active anaesthesiological intervention during the procedure - coincided with a 98.8% probability of the colonoscopy being completed.</p> <p>Conclusions</p> <p>With routine deep sedation, the colonoscopy completion rate nears the target performance for colonoscopic screening programs, at centers where colonoscopists of difference experience are employed in such programs. Organizing the daily workload to prevent negative factors affecting the success rate from occurring in combination may enable up to 85% of incomplete procedures to be converted into successful colonoscopies.</p
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